docs: def _sideral(date, longitude=0., model='mean', eop_correction=True, terms=106):
      """Get the sideral time at a defined date
  
      Args:
          date (Date):
          longitude (float): Longitude of the observer (in degrees)
              East positive/West negative.
          model (str): 'mean' or 'apparent' for GMST and GAST respectively
      Return:
          float: Sideral time in degrees
  
      GMST: Greenwich Mean Sideral Time
      LST: Local Sideral Time (Mean)
      GAST: Greenwich Apparent Sideral Time
      """
  
      t = date.change_scale('UT1').julian_century
  
      # Compute GMST in seconds
      theta = 67310.54841 + (876600 * 3600 + 8640184.812866) * t + 0.093104 * t ** 2\
          - 6.2e-6 * t ** 3
  
      # Conversion from second (time) to degrees (angle)
      theta /= 240.
  
      if model == 'apparent':
          theta += equinox(date, eop_correction, terms)
  
      # Add local longitude to the sideral time
      theta += longitude
      # Force to 0-360 degrees range
      theta %= 360.
  
      return theta